<template>
  <div class="spec-preview">
    <img :src="skuImageList[index]?.imgUrl" />
    <div class="event" @mousemove="showBigImg"></div>
    <div class="big">
      <img :src="skuImageList[index]?.imgUrl" ref="big" />
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
import { mapGetters } from 'vuex';

export default {
  name: 'Zoom',
  data() {
    return {
      index:0
    }
  },
  computed: {
    ...mapGetters(['skuImageList']),
  },
  methods: {
    showBigImg(event) {
      //获取mask蒙板的DOM元素
      const mask = this.$refs.mask;
      const big = this.$refs.big;
      //计算出小蒙板的left|top
      let x = event.offsetX - mask.offsetWidth / 2;
      let y = event.offsetY - mask.offsetHeight / 2;

      // 设置边距
      if (x <= 0) x = 0;
      if (x >= mask.offsetWidth) x = mask.offsetWidth;
      if (y <= 0) y = 0;
      if (y >= mask.offsetHeight) y = mask.offsetHeight;

      // 赋值给mask的left和top
      mask.style.left = x + 'px';
      mask.style.top = y + 'px';

      // 修改大图的left和big
      big.style.left = -2 * x + 'px';
      big.style.top = -2 * y + 'px';
    },
  },
  mounted() {
    // 挂载的时候,接收组件通信
    this.$bus.$on('changeIndex',(index)=>{
      this.index = index
    })
  },
};
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>
